Anaerobic Pathways Glycolysis Alternate Endpoints Gluconeogenesis

2/25/2015 Anaerobic Pathways Glycolysis • Lactate – common animal endpoint • Glycolysis – not a waste product – Glucose + 2 ATP → 4 ATP + 2 Pyruvate • No oxygen required • Fairly low energy yield • Lactate byproduct – Resting levels low – Tolerances 40 mmole/kg in humans, 200 mmole/kg in sea turtles – One alternative endpoint is Alanine. During strenuous exercise levels highest in muscle What organism uses that? When? and liver tissue Alternate Endpoints Gluconeogenesis – fate of end products • Lactate transferred to liver, converted back into glucose • Some animals use alternate • Cost of 6 ATP endpoints under some conditions • Why bother? – Goldfish use ethanol in cold, anoxic conditions – Glucose → pyruvate → acetalaldehyde → ethanol – Ethanol is excreted 1 2/25/2015 Review of some terms • Catabolic processes – Glycolysis – Glycogenolysis • Anabolic processes – Glycogenesis – Gluconeogenesis • Molecules – Glucose • Source and storage of glucose – Glucagon • Glycogen – glucose polymer – Pyruvate – Lactate – Hormone control: – Creatine phosphate – Insulin - stimulates storage of glucose in glycogen • Hormones How does the Atkins diet “work”? – Glucagon – reverse (glycogenolysis) – Insulin – Glucagon Oxygen in the Atmosphere 2 2/25/2015 Aerobic pathway Electron transfer system • Overview • From Glycolysis, pyruvate – Glucose + 36 ADP + 6 O2 → oxidation and Krebs cycle 2 36 ATP + 6 CO + 6 H2O – 1 glucose → 10 NADH + 2 • Glycolysis yields 2 pyruvate FADH2 • Convert pyruvate into acetyl- CoA (C2) • Krebs cycle • Electrons transferred to O2, – Combine with Oxaloacetate negatively charged oxygen (C4) to make Citrate (C6) combines with protons – Break off two carbons (metabolic water) (released as CO2) • Protons pumped out of – Yield (per pyruvate) mitochondrial matrix, setting • 2 CO2 • 3 NADH up a gradient • 1 FADH2 • ATP synthase converts ADP → • 1 GTP ATP as protons flow back into matrix Overview, ATP yields Alternative Fuels • Various amino acids can feed into parts of Krebs cycle +2 • Recall osmoregulation of intertidal copepod +2 +32 3 2/25/2015 Lipids - (CH2O)3(CH2)3n(CO2H)3 Lipids - (CH2O)3(CH2)3n(CO2H)3 • Greater oxygen demand to produce ATP, measured as respiratory quotient (RQ) • Common fuel for aerobic metabolism • Carbohydrate metabolism • Very high energy density – C6H12O6 + 6 O2 → 6 CO2 + 6 H2O • Chain of CH2 repeats – Ratio of CO2 to O2 is 1:1 • Saturated vs. unsaturated – RQ = 1.0 • Lipid metabolism (n=17) – (CH2O)3(CH2)51(CO2H)3→ 6 CO2 + 6 H2O – C57H111O9 + 80 O2 → 57 CO2 + 55 H2O – Ratio of CO2 to O2 is 57:80 ~ 0.67 – RQ = 0.7 Comparing fuels Patterns of Energy Use • The relative contribution of fuel types, duration and capacity are all variable. Metabolic water (g per KJ) • For example, general categories of muscle differ: 0.032 0.027 – Red muscle 0.022 • Lipid catabolism • High myoglobin, well supplied by vessels • Carbohydrates • Fatigue resistant • – Fast ATP yield, high ATP per unit oxygen, low Slow acting energy density – White muscle • Lipids • Carbohydrate catabolism – Slow ATP yield, low ATP per unit oxygen, high • Low myoglobin energy density • Fatigue quickly • Fast acting 4 2/25/2015 Ecological Implications • Migrating salmon • Short distance, fast flying insects – Begin migration using lipid – Rely on carbohydrates stores – Fast start, fast metabolism – Low duration – Infrequent burst acceleration involves carbohydrates • Long distance, slow flyers – Later in trip, protein – Lipids, more dense energy storage catabolism – Slower to metabolize • Humans • Flying locust energy requirements – High capacity for carbohydrate – 500 mg per hour glycogen metabolism and lactate – 70 mg per hour lipid turnover – Uses glycogen to initiate flight, switches to lipid – Carb-loading - maximize muscle glycogen stores Energy Storage Environment Animal Glucose Glycogen Very Short Term Low ATP demand, charge system +2 Creatine -6 ATP Diet High ATP demand, supply P Pyruvate Lipids Short Term Storage High – insulin, glycogenesis Blood Glucose Some Glycogen Levels Low – glucagon, glycogenolysis alternative Lactate Acetyl-CoA Amino Acids endpoints Long Term Storage Krebs + Electron Insulin - lipogenesis CO2 CO2 H2O Transport Chain Acetyl-CoA Lipids Epinephrine, glucagon - Lipolysis +34 O2 5 2/25/2015 • Animals use energy in hierarchy – Phosphagen system – Anaerobic – Aerobic 6.

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